One type of fuel flow arrestor (also known as an "overspeed governor" or "overspeed trip") for a diesel engine comprises a manually or automatically actuated valve for interrupting the flow of fuel to the fuel injectors which distribute fuel into the engine combustion chambers. The object of the valve is to "starve" the engine of its fuel supply if the engine enters an overspeed condition--the theory being that the engine will eventually run out of fuel and come to a stop, thus preventing possible damage to the engine. A disadvantage of such valves is that they only prevent the flow of additional fuel to the injectors which distribute fuel into the engine combustion chambers.
The fuel supply system for a large industrial diesel engine may include one or more fuel injectors for spraying fuel into each engine combustion chamber, an individual high pressure pump for supplying fuel to each fuel injector, a fuel supply gallery for supplying fuel to the high pressure pumps, and a conduit for conveying fuel from the engine fuel pump to the fuel supply gallery. "Valve" type fuel flow arrestors, as described above, are typically positioned in the conduit between the engine fuel pump and the fuel supply gallery. Accordingly, even after the valve is closed, a relatively large amount of fuel may remain in the high pressure pumps, the fuel supply gallery and the conduit. This remaining fuel will be sprayed by the injectors into the engine combustion chambers even though the valve has been closed. The remaining fuel (which may be as much as 2 pints) may be adequate to keep the engine running for as long as 5 minutes. If the engine has entered an overspeed condition, additional operation of the engine without any applied load may very quickly result in serious damage to the engine.
A second type of fuel flow arrestor comprises a control rod which is mechanically linked to each of the engine fuel injectors and which may be selectably positioned to vary the amount of fuel passing through the fuel injectors. If the engine enters an overspeed condition the control rod may be positioned to prevent the passage of additional fuel through the fuel injectors, again "starving" the engine of its fuel supply. However, the linkages which connect the control rod to the fuel injectors have been prone to jamming, which may inhibit positioning of the control rod to prevent additional fuel passing through the injectors, enabling the engine to run out of control.
An object of the present invention is to provide a fuel flow arrestor for an internal combustion engine which operates not only to shut off the flow of fuel from the engine fuel pump to the engine, but also restrains passage of fuel into the engine combustion chambers. In accordance with this object, the engine may be stopped very quickly because fuel which has accumulated in the engine fuel supply system is not permitted to enter the combustion chambers at all.